WO2002038012A2

WO2002038012A2 - Limited flow cup

Info

Publication number: WO2002038012A2
Application number: PCT/US2001/051171
Authority: WO
Inventors: Gerald Melsky; Jerry Porter; Andrea Burke; David Porat
Original assignee: Reliant Medical Products, Inc.
Priority date: 2000-11-13
Filing date: 2001-11-02
Publication date: 2002-05-16
Also published as: EP1341430A2; DE60130481T2; EP1341430B1; ATE372706T1; WO2002038012A3; AU2002235275A1; EP1341430A4; CA2428592A1; DE60130481D1

Abstract

A limited flow cup (10) is provided that includes an outer cup (12), and, in nested relationship with the outer cup (12), an inner cup (26) defining a fluid reservoir (38), the nested relationship of the outer cup and inner cup defining a metering chamber (42, 56) constructed to contain an amount of fluid that is delivered to the user during a single drinking motion.

Description

LIMITED FLOW CUP

RELATED APPLICATIONS

The subject matter of this patent application is related to that of U.S. S.N. 09/384,296, filed August 26, 1999, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD This invention relates to limited flow cups.

BACKGROUND

Dysphagia, a condition characterized by difficulty in swallowing food and liquids, can be present in patients suffering from stroke, head injury, neurological disorders, and other cognitive and motor problems. It may also occur as a result of aging, disability, or as a transient condition following some surgeries. As a result of dysphagia, patients may also suffer from dehydration and nutritional deficits.

When a person suffering from dysphagia attempts to swallow thin liquids, the bolus may tend to go down the bronchus and into the lungs, causing coughing, choking and even aspiration, which can lead to pneumonia. In order to maintain nutrition and hydration, these patients are sometimes given very small volumes, typically about one teaspoon. These smaller boluses can be more readily handled, often without aspiration problems.

Various devices, liquid thickeners and other products have previously been developed to assist patients with dysphagia, but these typically do not allow a fixed volume to be delivered, with a normal drinking motion, without the assistance of a caregiver. Limited flow drinking cups are designed to provide a fixed, metered amount of liquid to a user. A typical limited flow cup includes a cup body having a cover that defines an opening through which fluid can pass. Metering is provided by a three-piece assembly including (a) the cover, (b) a tube that is fixed to the cover at the opening and extends downward into the cup body, and (c) a tiny, self-contained metering cup mounted at the lower end of the tube. The metering cup has an open end that faces in a generally sideways direction. Prior to drinking, the cup body contains liquid up to a given liquid level, the metering cup is full of liquid, and the tube is filled with liquid up to the liquid level within the cup body. The metering cup and the portion of the tube that is below the liquid level in the cup body together αenne a metering chamber having a limited volume. When the user tilts the limited flow cup to a drinking position, the liquid within the metering chamber flows through the tube and out through the opening to the user. When the cup body is in the drinking position, the open end of the metering cup generally extends above the liquid level within the cup body, so that fluid cannot flow into the metering cup. As a result, only the volume within the metering chamber is dispensed during a single drinking motion.

SUMMARY

The present invention features a limited flow cup that has a metering chamber that is defined by a nested relationship between a pair of cups. The nested arrangement allows the metering chamber to be defined by components that do not include any closed features, such as tubes, and provides a device that does not include any small or moving parts. The lack of closed features allows the cups to be readily molded. Ease of molding is further facilitated by the simple shape of the cups, which allows them to release relatively easily from a mold. As a result, the limited flow cup is generally economical to manufacture, e.g.. by injection molding. The lack of small and moving parts allows the cup to be easily assembled both during manufacturing and prior to use by the user or a caregiver, and makes the cup relatively resistant to failure or damage. The cup is also easy for the user to correctly assemble and use. Additionally, the lack of closed features, which are typically difficult to clean, allows the limited flow cup to be kept clean and sanitary, e.g., by simply disassembling the nested cups and washing them in a dishwasher.

In one aspect, the invention features a limited flow cup, including an outer cup, and, in nested relationship with the outer cup, an inner cup defining a fluid reservoir, the nested relationsMp of the outer cup and inner cup defining a metering chamber, in fluid communication with the reservoir, constructed to contain an amount of fluid for delivery to a user during a drinking motion.

Implementations of the invention may include one or more of the following features. The metering chamber includes a cavity and an elongated fluid passage in fluid communication with the cavity. The cavity is defined by an indentation in a lower surface of the inner cup, and a lower surface of the outer cup. The elongated fluid passage is defined by a channel extending into the inner cup, and a ridge protruding from an inner wall of the outer cup. The cavity includes an opening to allow fluid to flow into the cavity from the reservoir. The opening is in a side surface of the cavity, and the opening extends to a lower surface of the inner cup to allow for delivery of essentially all of the liquid in the reservoir.

The limited flow cup further includes a cover that sealingly engages the rims of the inner and outer cups and defines an opening through which the user can drink the liquid. A lower surface of the cover defines an annular channel that, when the cover is in place, is in fluid communication with the metering chamber. The cover defines one or more apertures that communicate between the ambient air and the annular channel, allowing air to enter the annular channel. The cover further defines a drinking spout, and the aperture(s) allow sufficient air to enter the annular channel so that a user of the limited flow cup is hindered from withdrawing fluid from the limited flow cup by sucking on the drinking spout.

The volume of the metering chamber is from about 4.5 to 5.5 ml. The volume of the cavity is from about 3 to 5 ml. The volume of the elongated fluid passage is less than about 25% of the total volume of the metering chamber. The volume of the metering chamber is less than 10% of the volume of the inner cup. The amount of fluid delivered to the user when the inner cup is 10% full varies by no more than 25% from the amount of fluid delivered when the inner cup is 100% full. The cover defines a headspace volume that is from about 28% to 40% of the volume of the inner cup. The amount delivered to the user when the reservoir is 100% full will be less than or equal to the volume of the metering chamber. Also, the amount delivered to the user immediately after the reservoir is initially filled by the user will be less than or equal to the volume of the metering chamber.

The outer cup and inner cup include corresponding structures that prevent the outer cup from being used without the inner cup in nested arrangement with the outer cup. For example, the outer cup includes an aperture in a lower surface of the outer cup, through which liquid will flow if the outer cup is filled with liquid without the inner cup in nested arrangement with the outer cup, and the inner cup includes a plug extending from its lower surface, the plug being positioned to seal the aperture in the lower surface of the outer cup when the inner and outer cups are properly nested. Alternatively, the aperture in the outer cup includes a raised rim, and the inner cup includes a recess that is constructed to seal around the raised rim and over the aperture when the inner and outer cups are properly nested. In another aspect, the invention features a limited flow cup for dispensing a limited volume of liquid to a user each time the limited flow cup is tilted to a drinking position, the limited flow cup including: (a) an outer cup, (b) an inner cup, nested within the outer cup. for containing a supply of the liquid, and (c) a cover that is constructed to be sealingly applied to the outer cup and inner cup, the cover including an aperture through which the liquid can be delivered to the user. The outer cup and inner cup have adjacent spaced surfaces that together define a metering chamber that includes a cavity, and an elongated fluid passage in fluid communication between the cavity and the aperture, the cavity including an inlet mrough which fluid can flow from the inner cup to the cavity. The inlet is positioned so that it will be above the liquid level in the inner cup when the inner cup is tilted sufficiently to allow fluid to flow from the aperture.

In a preferred implementation of this aspect of the invention, a lower surface of the cover defines an annular channel that, when the cover is in place, is in fluid communication with the metering chamber. The cover further defines a drinking spout, and one or more apertures that communicate between the ambient air and the annular channel, allowing air to enter the annular channel, the aperture(s) allowing sufficient air to enter the annular channel so that a user of the limited flow cup is hindered from withdrawing fluid from the limited flow cup by sucking on the drinking spout.

In yet another aspect, the invention features a limited flow cup including a pair of nesting inner and outer cups, the inner and outer cups being constructed to be nested and disassembled by a user, allowing easy cleaning, and the nested arrangement of the cups defining a fluid passage that does not exist when the cups are disassembled.

In preferred implementations, the inner and outer cups do not include any closed features.

Preferred limited flow cups of the invention include an "anti-suck" feature (e.g., the apertures in communication with the annular channel, described above) that impedes the user from circumventing the metering function by sucking fluid out of the cup. Thus, in such cups the metering feature generally cannot be circumvented by applying mouth suction to the hole in the lid of the cup through which the user drinks.

Preferred cups do not require the person filling the cup with liquid to follow any special or non-obvious steps, such as filling the cup so that liquid stays below a fill line or mark on the cup, steps which may be difficult for caregivers to remember. Such preferred cups are also designed to meter fluid even when filled to the rim of the cup, while still maintaining an aesthetic cup shape, as will be discussed in detail below. The ability of the cup to function properly when filled to the rim ensures that a metered volume will be delivered each time the user drinks from the cup, including the first drink when the cup is at its fullest. This assurance of first-pour functioning is very important in dysphagia applications, due to the grave consequences that may result from receiving too large a volume of liquid even once.

In some implementations, the assembled cup is generally spill-proof, with only a single metered volume of liquid exiting the cup when it is inadvertently knocked on its side.

Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

Fig. 1 is a perspective view of a cup according to one embodiment of the invention. Figs. 1 A-1C are front, top and side plan views, respectively.

Figs. 2 and 2 A are cross-sectional views of the cup of Fig. 1, taken along line A- A of Fig. 1A. In Fig. 2, the cup is in an upright position. In Fig. 2 A the cup is shown in a tipped, drinking position.

Figs. 3, 3 A and 3B are exploded perspective views of the cup of Fig. 1, taken from different angles.

Figs. 4 and 4A are schematic cross-sectional views illustrating alternate structures for preventing the use of the outer cup as a drinking cup.

DETAILED DESCRIPTION

Referring to Fig. 1, limited flow cup 10 includes an outer cup 12 including a generally cylindrical side wall 54 and a generally flat bottom surface 52 (Fig. 3). A pair of handles 16 extend from side wall 54. A cover 14 is constructed to be sealingly attached to the outer cup 12. As shown in Figs. 1A and IB, the cover 14 includes a drinking spout 18 having an aperture 20 through which a user of the cup can sip a liquid. The cover also includes a vent hole 22 to allow air to enter the cup as fluid is depleted and thereby allows liquid to flow out of the inner cup unimpeded, and three "anti-suck" holes 24, the function of which will be discussed below.

Referring to Fig. 3, the limited flow cup 10 further includes a generally cylindrical inner cup 26 that is slightly smaller in outer diameter than the inner diameter of the outer cup 12, and slightly shorter than outer cup 12, so that the inner cup 26 can be received within the outer cup 12 in nested engagement as shown in Fig. 2. A clearance of 0.005 to 0.010 inches would ensure that the cups could be easily nested and un-nested and at the same time ensure that very little liquid-holding volume is created between the cups. The inner cup 26 fits snugly within the outer cup 12, and defines a reservoir 38 for holding a liquid. The inner and outer cups include structural features that together define a metering chamber when the cups are nested, as will be discussed below.

As shown in Fig. 3, the inner cup 26 includes a generally flat bottom surface 44 and a generally cylindrical side wall 48, having a locally flat portion 49. A disc-shaped cavity 42 is formed by an indentation 64 in bottom surface 44. A channel 46, defined by a diagonally cut groove in the inner cup 26, defines a triangular volume extending from the cavity 42 up the outer side wall 48 of the inner cup. (Seen from above, in Figs. 3 A and 3B, the cavity 42 and channel 46 look like a protrusion 42' and a ridge 46', respectively.)

As shown in Fig. 3B, the inner surface of outer cup 12 includes an elongated generally triangular ridge 50 that extends along part of the bottom surface 52 and extends up the inner surface of side wall 54 of the outer cup 12.

When the inner cup 26 and outer cup 12 are nested (as shown in Figs. 2-2A), the cavity 42 is closed from below by the generally flat bottom surface 62 of the outer cup 12. Ridge 50 nests within channel 46 (Fig. 3), filling most of the volume of the channel, i.e., the width of the ridge is nearly that of the channel, so that a seal will be formed between the ridge and channel. The ridge 50 is slightly shorter than the depth of the channel, so that an elongated fluid passage 56 (Fig. 2) is defined between the "hypotenuse" or top surface 59 of the ridge and the upper wall 58 of the channel. Elongated fluid passage 56 extends diagonally from the cavity 42, with which it is in fluid communication, to the rim 60 of the nested inner and outer cup assembly. The elongated fluid passage 56 ends in an open terminus 57 at rim 60. The cavity 42 communicates with the inside of inner cup 26 by way of an aperture 66 in the wall 68 of cavity 42 that is located diametrically opposite the inlet of elongated fluid passage 56.

In addition to defining the metering chamber, the engagement of ridge 50 with channel 46 self-aligns the inner and outer cups, so that the limited flow cup is easy for a caregiver or patient to assemble correctly.

When the cup is in its upright position, shown in Fig. 2, liquid 40 flows into cavity 42 through aperture 66, until the cavity 42 is full and liquid is also present in the elongated fluid passage 56 up to the liquid level L. The cavity 42 and elongated fluid passage 56 together define a metering chamber. The total volume of liquid that is in the metering chamber when the device is tipped to a drinking position (Fig. 2 A) is the volume of liquid that will be delivered to the user through aperture 20. The volume delivered to the user will vary slightly as the liquid level in the cup drops, due to the reduced volume of liquid that will be present in the elongated fluid passage 56. The volume of the cavity is much larger than that of the elongated fluid passage (generally the ratio of the volume of the elongated fluid passage to that of the cavity is about 1 :4 to 1 :10). As a result, the volume of the cavity dominates, and the user will receive essentially the same amount of liquid regardless of the level of fluid in the elongated passage, which will be reduced as the liquid in the cup is depleted. It is also noted that the user may not receive the entire volume present in the metering chamber, depending on the angle to which the user tips the device (e.g., it may be necessary to tip the device well beyond the angle shown in Fig. 2A (generally to about 90 degrees from the position shown in Fig. 2) to receive the entire volume in the metering chamber.)

As discussed above, cover 14 includes a drinking spout 18. Spout 18 is located diametrically opposite the cavity 42, to properly orient the cup as will be discussed below. The spout extends relatively high above the upper surface of the cover, and joins with the cover in a smootWy curved surface, to allow the user to drink from the cup without tilting his head back, i.e., to drink in what is sometimes referred to as a "chin tuck" position. This position is generally thought to be a safer drinking position for patients suffering from dysphagia. The cover 14 is also quite tall, relative to the height of the inner and outer cups, for reasons which will be explained below. Cover 14 also includes a generally cylindrical outer sleeve 28 that is coextensive with the outer surface of the cover and is dimensioned to engage rim 30 of cup body 12 in an interference engagement. Cover 14 also includes, extending downwardly from its inner top surface, a generally cylindrical inner sleeve 32 that is generally coaxial with the outer sleeve 28. Inner sleeve 32 is dimensioned to fit within and sealingly engage the inner wall 34 of inner cup 26 to provide a fluid-tight seal. To allow the cover to be easily snapped onto the nested inner and outer cups, and to facilitate fluid-tight sealing, the cover is preferably formed of a resilient material.

An annular channel 65 is defined between the outer wall 67 of the cover and the inner sleeve 32 (see Figs. 2 and 3). This annular channel 65 is in fluid communication with the open terminus 57 of the elongated fluid passage 56, and also with aperture 20 in the spout 18. Thus, during drinking (Fig. 2A), fluid flows from the elongated fluid passage 56, into the annular channel 65, and through aperture 20 to the user. As shown in Fig. 3, a portion 31 of the inner sleeve 32 is flattened, to provide a relatively large volume in the area of the annular channel that is adjacent terminus 57, allowing good flow of fluid to the aperture 20. The flattened portion 31 of the inner sleeve 32 is also geometrically similar to a flat surface 29 (Fig. 3B) on the inside of the inner cup 26, adjacent to the open terminus 57 of the elongated fluid passage 56, thereby allowing surface 31 of the inner sleeve 32 to seal to surface 29 of the inner cup 26.

Annular channel 65 also communicates with "anti-suck" holes 24. The "anti-suck" holes 24 allow air to pass into the annular channel 65 in the event that the user sucks on the spout 18, in an attempt to aspirate liquid from the device without tilting the device to a drinking position and thereby activating the limited flow function (discussed below). The "anti-suck" holes 24 prevent the pressure in the annular channel 65 from being lowered sufficiently for fluid to be drawn up into the spout 18, thereby preventing the user from circumventing the limited flow function of the cup. It is preferred that the cover include a plurality of "anti-suck" holes, as shown, rather than a single hole, because it is unlikely that a user would inadvertently cover multiple holes with a finger during use of the cup.

Preferably, the inner and outer cups and the cover are formed by injection molding. Suitable materials for the inner and outer cup include thermoplastic polymers such as polyethylene, polypropylene, polyamides, such as Nylon, and polycarbonate. Thermosets may also be used. Suitable materials for the cover include relatively compliant thermoplastic polymers, such as polypropylene, polyethylene, polyurethanes, plasticized polyvinyl chloride (PVC), and thermoplastic elastomers (TPEs).

When the cup is to be used, the inner cup is nested within the outer cup, and the inner cup is filled with a liquid to or above a fill line (not shown) on its inner wall 34. (The fill line indicates the amount of liquid that should be added in order for the cup to initially contain the advertised volume of the cup, e.g., 8 fluid ounces.) The inner cup 26 can be filled up to its rim, if desired, without any problems in metering of the liquid 40, for reasons that will be discussed below. The fill line is preferably 1/8 to 3/8 inch below the rim, so that the cup may be filled with its advertised volume and the lid snapped in place without spilling liquid from the cup. Once the inner cup is filled, the cover 14 is then snapped onto the cup assembly, so that the cover and the rims of the inner and outer cups are in sealing engagement. As shown, e.g., in Fig. 3B, the top surface 59 of the ridge 50 is slightly convex, as is the corresponding upper wall 58 of channel 46. The curvature of surface 59 allows surface 59 to be relatively vertical near the rim of outer cup 12, and, similarly, the curvature of wall 58 allows wall 58 to be relatively vertical near the rim of inner cup 26. These vertical surfaces, and the relatively small interruption of the circularity of the rims of the inner and outer cups facilitates the sealing engagement of the inner and outer sleeves of the cover 14 with the rims of the cups. To drink from the device, the user places the spout 18 to his lips and tilts the cup in a normal drinking manner. When the user tips the cup to a drinking position, as shown in Fig. 2A, the volume of liquid in the metering chamber is delivered to the user through aperture 20. As the cup is tipped to a drinking position, liquid flows within the inner cup 26 so that level L' remains horizontal. The inner cup and cover are dimensioned, and the cavity 42 and aperture 66 are oriented, so that before the angle of tilt of the cup is such that liquid will flow out of the spout 18 (typically at least about 30 degrees from the horizontal) the aperture 66 will be exposed above the liquid level L' in the inner cup 26, as shown in Fig. 2A. Because the aperture 66 is above the liquid level L', liquid will not flow into aperture 66 when the cup is tilted further for drinking, and thus the user will receive only the volume of liquid in the metering chamber, as discussed above. To drink more liquid, the user must return the cup to its upright (or nearly upright) position, allowing the user time to swallow the predetermined volume of liquid. Because spout 18 is located diametrically opposite the cavity 42, as discussed above, the user will always orient the cup so that the aperture 66 will be above the liquid level during drinking, as shown in Fig. 2A.

It is important that the limited flow cup perform its metering function the first time (and every subsequent time) that the cup is used, and that it perform the metering function regardless of how full the inner cup 26 is filled. In other words, it is important that the limited flow function of the cup not be circumvented by over-filling the inner cup 26, and that the amount of liquid dispensed to the user never exceed the maximum volume of the metering chamber. Preferably, the amount of liquid dispensed to the user is approximately same (e.g., vary by no more than 25%) whether the inner cup is 10% full or 100% full. In order for the metering function to be performed every time the cup is used, regardless of the fill level, two conditions must be met: (a) there must be a sufficient volume of air within the cup to allow the liquid to flow to the position shown in Fig. 2 A when the cup is tilted, and (b) there must be sufficient open area in the cover on the spout side to allow all of the liquid in the cup (up to the maximum volume that the inner cup can contain) to be below line L' in Fig. 2A when the cup is inclined at an angle at which fluid first begins to flow out of the aperture 20.

The first condition can be met by making the cover 14 is quite tall, relative to the height of the inner and outer cups, as shown in the figures. As a result of the height of the cover, the inner sleeve 32 and wall 36 together define a relatively large open volume or "headspace" that cannot be filled with liquid when the user fills the inner cup. This headspace allows the liquid to be displaced within the cup as shown in Fig. 2A when the cup is tilted (i.e., allows the cup to meet condition (a), above). For the cover geometry shown in Figs. 2-2A, the volume of the headspace defined by the cover is generally about 28% to 40% of the volume of the inner cup. However, the total headspace volume required to satisfy both conditions will depend upon the geometry of the cover, e.g., the total volume required will be less if the volume defined by the drinking spout (the volume on the side of the cup into which the liquid flows when the cup is tilted to drink) is increased. In order to satisfy condition (b), it is important that, of the total volume of the headspace, a sufficient amount is disposed on the side of the cup into which the liquid flows when the cup is tilted to drink so that the level of the liquid will never be above line L' when the cup is tilted to the angle at which liquid will begin to flow out of aperture 20. Also, for a given headspace, the higher the spout extends above the cover, the greater will be the tip angle required before liquid will flow from the aperture 20. The extra volume created by an extended drinking spout is created mostly in the annular volume, where it does not alter the fluid level dynamics in the volume enclosed by the inner cup and the headspace inside the lid's inner partition.

For a cup having an advertised volume of 8 fluid ounces, the preferred dimensions of the cup are as follows: the inner diameter of the inner cup 26 is from about 3.0 to 3.5 inches, the diameter of the inner sleeve of the cover is the same as the inner diameter of the inner cup 26, the height of the inner cup is from about 1.5 to 2.5, the height of the cover (exclusive of the spout) is from about 0.75 to 1.25 inches, and the height of the spout above the top of the cover is about 0.75 to 1.25 inches. The volume of the cup may be altered, e.g., by scaling all dimensions proportionally.

Other embodiments are within the scope of the following claims.

It is generally desirable to prevent the user of the limited flow cup, or a caregiver, from circumventing the metering feature of the limited flow cup by using the outer cup 12 alone, without the inner cup 26. This may be accomplished in a variety of ways, as will be apparent to those skilled in the art. Two examples are illustrated in Figs. 4 and 4A. As shown in Fig. 4, the outer cup 12 may include an aperture 100 in its lower surface, and the inner cup 26 may include a plug 102 that seals the aperture 100 when the cups are properly nested. Alternatively, as shown in Fig. 4A, the outer cup 12 may include a bore 104 having a rim 106, and the inner cup 26 may include an annular recess 108 that is constructed to fit sealingly over the rim 106.

For example, the cavity need not be disc-shaped, but could be square, rectangular, or any other desired shape. The ridge in the outer cup can be omitted, and the channel defined by a groove in the inner cup and a cylindrical inner wall of the outer cup. Also, while the ridge is shown and described as having a slightly curved "hypotenuse", the ridge may be more triangular in shape. Many other alterations of the structural features of the inner and outer cup may be made, provided that the nested arrangement of the inner and outer cup defines the metering chamber. The cup has been shown as having two handles. However, in other embodiments the cup may have a single handle or no handle. While the cover has been shown and discussed as being relatively tall, and having a tall, curved spout, many other cover designs may be used. Suitable cover geometries will depend upon the volume of the cup and the application in which it will be used, as will be readily understood by those skilled in the art.

The cup may be used in many applications, other than by dysphagia sufferers, e.g., as a travel coffee mug, as an infant "dripless" cup, or as a disposable container for beverages such as nutritional drinks. When the cup is used to dispense hot beverages, the double- walled construction may afford a degree of thermal insulation. Depending on the application, the volume of the cavity may vary widely, e.g., from 1 to 20 ml.

Claims

WHAT IS CLAIMED IS:

1. A limited flow cup, comprising an outer cup, and, in nested relationship with the outer cup, an inner cup defining a fluid reservoir, the nested relationship of the outer cup and inner cup defining a metering chamber, in fluid communication with the reservoir, constructed to contain an amount of fluid for delivery to a user during a drinking motion.

2. The limited flow cup of claim 1 wherein said metering chamber comprises a cavity and an elongated fluid passage in fluid communication with the cavity.

3. The limited flow cup of claim 2 wherein the cavity is defined by an indentation in a lower surface of the inner cup, and a lower surface of the outer cup.

'4. The limited flow cup of claim 2 wherein the elongated fluid passage is defined by a channel extending into the inner cup, and a ridge protruding from an inner wall of the outer cup.

5. The limited flow cup of claim 2 wherein the cavity includes an opening to allow fluid to flow into the cavity from the reservoir.

6. The limited flow cup of claim 5 wherein the opening is in a side surface of the cavity, and the opening extends to a lower surface of the inner cup to allow for delivery of essentially all of the liquid in the reservoir.

7. The limited flow cup of claim 1 further comprising a cover that sealingly engages the rims of the inner and outer cups and defines an opening tMough which the user can drink the liquid.

8. The limited flow cup of claim 7 wherein a lower surface of the cover defines an annular channel that, when the cover is in place, is in fluid communication with the metering chamber.

9. The limited flow cup of claim 8 wherein the cover defines one or more apertures that communicate between the ambient air and the annular channel, allowing air to enter the annular channel.

10. The limited flow cup of claim 9 wherein the cover further defines a drinking spout, and the aperture(s) allow sufficient air to enter the annular channel so that a user of the limited flow cup is hindered from withdrawing fluid from the limited flow cup by sucking on the drinking spout.

11. The limited flow cup of claim 1 wherein the volume of said metering chamber is from about 4.5 to 5.5 ml.

12. The limited flow cup of claim 2 wherein the volume of said cavity is from about 3 to 5 ml.

13. The limited flow cup of claim 2 wherein the volume of said elongated fluid passage is less than about 25% of the total volume of the metering chamber.

14. The limited flow cup of claim 1 wherein the volume of the metering chamber is less than 10% of the volume of the inner cup.

15. The limited flow cup of claim 1 , wherein the amount of fluid delivered to the user when the inner cup is 10% full varies by no more than 25% from the volume delivered when the inner cup is 100% full.

16. The limited flow cup of claim 7 wherein the cover defines a headspace volume that is from about 28% to 40% of the volume of the inner cup.

17. The limited flow cup of claim 1 wherein the amount delivered to the user when the reservoir is 100% full will be less than or equal to the volume of the metering chamber.

18. The limited flow cup of claim 1 wherein the amount delivered to the user immediately after the reservoir is initially filled by the user will be less than or equal to the volume of the metering chamber.

19. The limited flow cup of claim 1 wherein the outer cup and inner cup include corresponding structures that prevent the outer cup from being used without the inner cup in nested arrangement with the outer cup.

20. The limited flow cup of claim 19 wherein the outer cup includes an aperture in a lower surface of the outer cup, through which liquid will flow if the outer cup is filled with liquid without the inner cup in nested arrangement with the outer cup.

21. The limited flow cup of claim 20 wherein the inner cup includes a plug extending from its lower surface, the plug being positioned to seal the aperture in the lower surface of the outer cup when the inner and outer cups are properly nested.

22. The limited flow cup of claim 20 wherein the aperture in the outer cup includes a raised rim, and the inner cup includes a recess that is constructed to seal around the raised rim and over the aperture when the inner and outer cups are properly nested.

23. A limited flow cup for dispensing a limited volume of liquid to a user each time the limited flow cup is tilted to a drinking position, the cup comprising: an outer cup, an inner cup, nested within the outer cup, for containing a supply of the liquid, and a cover that is constructed to be sealingly applied to the outer cup and inner cup, the cover including an aperture tMough which the liquid can be delivered to the user, the outer cup and inner cup having adjacent spaced surfaces that together define a metering chamber that includes a cavity, and an elongated fluid passage in fluid communication between the cavity and the aperture, the cavity including an inlet tMough which fluid can flow from the inner cup to the cavity, the inlet being positioned so that it will be above the liquid level in the inner cup when the inner cup is tilted sufficiently to allow fluid to flow from the aperture.

24. A limited flow cup for dispensing a limited volume of liquid to a user each time the limited flow cup is tilted to a drinking position, the limited flow cup comprising: an outer cup, an inner cup, nested within the outer cup, for containing a supply of the liquid, and a cover that is constructed to be sealingly applied to the outer cup and inner cup, the cover including an aperture tMough which the liquid can be delivered to the user, the outer cup and inner cup having adjacent spaced surfaces that together define a metering chamber that includes a cavity, and an elongated fluid passage in fluid communication between the cavity and the aperture, the cavity including an inlet tMough which fluid can flow from the inner cup to the cavity, the inlet being positioned so that it will be above the liquid level in the inner cup when the inner cup is tilted sufficiently to allow fluid to flow from the aperture, a lower surface of the cover defining an annular channel that, when the cover is in place, is in fluid communication with the metering chamber, the cover further defining a drinking spout, and one or more apertures that communicate between the ambient air and the annular channel, allowing air to enter the annular channel, the aperture(s) allowing sufficient air to enter the annular channel so that a user of the limited flow cup is hindered from withdrawing fluid from the limited flow cup by sucking on the drinking spout.

25. A limited flow cup comprising a pair of nesting inner and outer cups, the irmer and outer cups being constructed to be nested and disassembled by a user, allowing easy cleaning, and the nested arrangement of the cups defining a fluid passage that does not exist when the cups are disassembled.

26. The limited flow cup of claim 25 wherein the inner and outer cups do not include any closed features.